1. Technical Field
This invention relates generally to digital color copiers, and more particularly to such copiers capable of processing a color image signal to reproduce a given color as a different color.
2. Background Art
U.S. Pat. No. 4,204,728, which issued to Goshima et al. on May 27, 1980, discloses an optical copier which uses color filters to produce color separation electrostatic images on a photosensitive medium for development with cyan, magenta and yellow toners. Color conversions are effected by selection of proper filter combinations, but all colors of the original except for the three monochromatic elements yellow, magenta, and cyan will be reproduced in different colors from those of the original. It is impossible to replace only a particular color with another.
U.S. Pat. No. 4,538,182, which issued to S. Saito et al. on Aug. 27, 1985, discloses a copier which reproduces a plurality of particular colors, for example red and black, in which the original red will be changed to black or the original black will be changed to red. However, it is impossible to change a color containing a plurality of color components to another.
U.S. Pat. No. 4,855,765, which issued to Suzuki et al. on Aug. 8, 1989, discloses a digital color copier which can replace a selected particular color in an origial with a desired designated color. The color to be replaced and the replacing color can be selected from a pre-set list or 24 different colors stored in ROM. This has the drawback of limiting the selectable colors to only those pre-programmed into the ROM. In another embodiment of the Suzuki et al. patent, signals representing the color to be replaced are stored in RAM during a preliminary scan. When the stored color signals do not coincide with color input image signals read during a subsequent scan, the input signals are printed unchanged. When the stored color signals coincide with the input image signals, the input signals are replaced with signals of another designated color. This second embodiment requires two scans; one to store the color to be replaced, and one to read the image.
A copier's life is in part limited by the physical number of times the image is scanned, and the inconvenience of the operators is measured in part by the time duration they must wait to remove the original after pressing the start button. A copier which requires only a single scan to determine the color to be replaced, to determine the replacing color, and to read the image data would be very preferable to a copier which requires two or more scans for the same functions.